1. Field of the Invention
The present invention relates to a substrate processing apparatus configured to perform an etching process or a film forming process on the surface of a substrate such as a semiconductor wafer, and a method of manufacturing a semiconductor device.
2. Description of the Prior Art
As an example of substrate processing apparatuses, a semiconductor manufacturing apparatus is known, and as an example of semiconductor manufacturing apparatuses, a vertical diffusion chemical vapor deposition (CVD) apparatus is known. Such a vertical diffusion CVD apparatus includes a narrow and long vertical buffer chamber at a position close to the inner wall of a reaction tube configured to process a substrate, and in the buffer chamber, discharge electrodes and a gas nozzle are provided in astute where the discharge electrodes are surrounded by two dielectric tubes. High-frequency power generated by an oscillator is applied across ends of the discharge electrodes so as to generate plasma between the discharge electrodes disposed in the buffer chamber, and reactive gas supplied through the gas nozzle is excited by the plasma and is supplied to a target film located in a process chamber through a gas supply hole formed in the wall of the buffer chamber (refer to Patent Document 1).    [Patent Document 1] Japanese Patent No. 3,947,126
Although the discharge electrodes are vertically extended so as to generate plasma uniformly at the inside of the buffer chamber, the discharge electrodes can expand or shrink due to the influence of heat of a heater. In this case, plasma is non-uniformly generated, and thus the film thickness of a process-target substrate becomes non-uniform. However, there no effective means for checking shape variations of the discharge electrodes in the conventional art, and in many cases, shape variations of the discharge electrodes are detected only after the film thickness of the process-target substrate has become non-uniform.